Why the White Brain Matters. Given the crossword puzzle clue “brain stuff,” what would come to your mind? Quite a few readers might answer “gray matter” and with reason. In common parlance, gray matter has become virtually synonymous with the brain, as when Agatha Christie’s famous detective Hercule Poirot boasts about his “little gray cells.” Much of neuroscience, as presented today, tends to reinforce this view that the gray matter of the brain’s cerebral cortex makes possible our distinctive mental capacities, such as memory, language, thought, and emotion. Yet, a glance at the anatomy of the human brain reveals that cortical gray matter comprises only the brain’s outermost one to four millimeters, a layer about the thickness of heavy cloth, over a brain that in the average human adult weighs three pounds. Almost one half of the brain’s volume is not gray but white matter, the densely packed collection of myelinated (insulated) projections of neurons that course between widely dispersed gray matter areas.
If gray matter supposedly “is” the brain, then what is all this white matter doing in our heads? Only quite recently have neuroscientists in the laboratory and clinic begun to understand the importance of this long- neglected part of the brain. In the normal brain, white matter appears to provide the essential connectivity, uniting different regions into networks that perform various mental operations. We know this because, when this connectivity is disrupted by disease or other damage to white matter, the result is often a dramatic disturbance of normal mental function. The scope and variety of syndromes that result from disruption of white matter suggest that white matter makes a pivotal contribution to all realms of human behavior, a contribution we are just beginning to fathom. So diverse and important are these contributions that it is time to consider the need for a new ﬁeld: the behavioral neurology of white matter. THE DISCOVERY (AND “REDISCOVERY”) OF WHITE MATTERIn 1.
SUMMARY: Ischemia of the spinal cord is a rare entity with a poor prognosis. Brain ischemia is no longer a diagnostic challenge; on the contrary, ischemia of the. Trzepacz PT, Yu P, Sun J, Schuh K, Case M, Witte MM, Hochstetler H, Hake A; Alzheimer's Disease Neuroimaging Initiative: Comparison of neuroimaging modalities for the.
De Humani Corporis Fabrica, the Renaissance anatomist Andreas Vesalius was the ﬁrst to distinguish clearly between white matter and the gray matter that overlay regions of the cerebral cortex. Only with time, though, did the role of white matter in providing structural and functional connections between gray matter areas within the brain become apparent. In the 1. 9th century, the Parisian physician Jean Martin Charcot greatly advanced understanding of white matter’s role with his detailed studies of multiple sclerosis (MS), a disease of young adults characterized by primary damage to the white matter of the central nervous system. At the turn of the 2. Sigmund Freud turned biomedical thinking toward psychoanalytic explanations of behavior, and for more than 5.
In 1. 96. 5, however, Norman Geschwind, M. D., proposed that one mechanism underlying dysfunctional brain- behavior relationships might be cerebral disconnection, a view that pointed directly at the need to study white matter lesions. Geschwind’s seminal article advanced the view that the dense connectivity of the brain underlay its mental operations. Central to his concept was the idea that an intricate web of white matter pathways course within and between the brain’s hemispheres. White matter is a vast, intertwining system of neural connections that join all four lobes of the brain (frontal, temporal, parietal, and occipital), and the brain’s emotion center in the limbic system, into the complex brain maps being worked out by neuroscientists.
All of the well- known cortical areas such as Broca’s area, Wernicke’s area, the prefrontal cortex, and the hippocampus are connected by white matter tracts to other regions of the brain. This suggests that the cortical regions act in concert to perform mental operations and no cortical area acts in isolation. Without functioning white matter, the brain could be like a group of people in proximity to each other but unable to communicate with each other. After centuries of being recognized but not well understood, white matter gained growing importance as neuroscientists turned to the study of brain- behavior relationships. At the beginning of the 2. This theory has reinforced the idea that the connectivity provided by white matter occupies a central place in the elaboration of human behavior. The impressive growth of modern neuroimaging has let us depict white matter and its functional specializations in increasingly elegant detail.
- SUMMARY: Susceptibility-weighted imaging (SWI) has continued to develop into a powerful clinical tool to visualize venous structures and iron in the brain and to.
- Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system and is the most common cause of neurologic disability in young adults.
- Conventional and Advanced MRI Features of Pediatric Intracranial Tumors: Posterior Fossa and Suprasellar Tumors.
Today, there is an explosion of information on white matter, its role in normal brain function, and its relevance to human illness. EFFICIENT BRAIN SIGNALINGIn contrast to gray matter, in which the cell bodies of neurons predominate, the term white matter refers to areas of the brain where there is a preponderance of axons coated with myelin.
Susceptibility- Weighted Imaging: Technical Aspects and Clinical Applications, Part 2. Abstract. SUMMARY: Susceptibility- weighted imaging (SWI) has continued to develop into a powerful clinical tool to visualize venous structures and iron in the brain and to study diverse pathologic conditions.
SWI offers a unique contrast, different from spin attenuation, T1, T2, and T2* (see Susceptibility- Weighted Imaging: Technical Aspects and Clinical Applications, Part 1). In this clinical review (Part 2), we present a variety of neurovascular and neurodegenerative disease applications for SWI, covering trauma, stroke, cerebral amyloid angiopathy, venous anomalies, multiple sclerosis, and tumors. We conclude that SWI often offers complementary information valuable in the diagnosis and potential treatment of patients with neurologic disorders. Susceptibility- weighted imaging (SWI) is a fully velocity- compensated high- resolution 3. D gradient- echo sequence that uses magnitude and filtered- phase information, both separately and in combination with each other, to create new sources of contrast. With the advent of parallel imaging and the greater availability of clinical 3. T MR images, it is now possible to image the entire brain with SWI in roughly 4 minutes.
SWI has been found to provide additional clinically useful information that is often complementary to conventional MR imaging sequences used in the evaluation of various neurologic disorders, including traumatic brain injury (TBI), coagulopathic or other hemorrhagic disorders, vascular malformations, cerebral infarction, neoplasms, and neurodegenerative disorders associated with intracranial calcification or iron deposition. As neuroradiologists become more aware of these various applications and as advances in software technology permit easier acquisition and better interpretation, SWI will likely be incorporated into the routine diagnostic imaging evaluation. The technical concepts of SWI were outlined in Part 1 of this 2- part review and would be valuable reading as background to this article, especially the discussion about magnitude, SWI filtered phase, SWI processed data, and contrast available in SWI. The following sections discuss different clinical applications of SWI predominantly in adults. An excellent clinical review by Tong et al. American Journal of Neuroradiology already covers many SWI applications in children. TBI: Diffuse Axonal Injury.
TBI is a major cause of morbidity, mortality, disability, and lost years of productive life throughout the world. CT remains the primary imaging technique for the initial evaluation of patients who have sustained head trauma because it effectively allows detection of intracranial hemorrhages that require acute neurosurgical intervention. In recent years, however, MR imaging has been gaining popularity as an adjunctive imaging method in patients with TBI because it permits more precise identification and localization of smaller hemorrhages and can provide useful information regarding mechanisms of injury and potential clinical outcome. SWI is particularly helpful for the evaluation of diffuse axonal injury (DAI), often associated with punctate hemorrhages in the deep subcortical white matter, which are not routinely visible on CT or conventional MR imaging sequences.
SWI exploits the magnetic susceptibility differences between tissues, resulting in phase differences between regions containing paramagnetic deoxygenated blood products (deoxyhemoglobin, intracellular methemoglobin, and hemosiderin) and surrounding tissue. Who Is Ray J Dating on this page. The signal- intensity cancellation in the magnitude images and the additional suppression from the SWI filtered- phase images produce a hypointense signal in areas of acute and early subacute hemorrhage.
Studies by Tong et al. Babikian et al. 6 have shown that SWI is 3–6 times more sensitive than conventional T2*- weighted gradient- echo (T2*GE) sequences in detecting the size, number, volume, and distribution of hemorrhagic lesions in DAI. Figure 1 shows a woman who was involved in a motor vehicle crash and sustained severe head injuries resulting in a coma. A nonenhanced CT scan showed suspicious low attenuations in the damaged areas. As expected, the cerebral lesions were more clearly visualized on T1- and T2- weighted images. SWI was even more strikingly sensitive in detecting the abnormalities and showed a much greater number and larger size of lesions compared with other conventional sequences.
Furthermore, the shape of the lesions was more clearly delineated in the left cerebellar hemisphere, indicating the presence of shearing, often considered a cause of DAI. Fig 1. A 3. 8- year- old woman who sustained severe TBI following a motor vehicle crash and lapsed into a coma. CT and MR images were obtained on the second day of hospitalization. A, Nonenhanced CT scan shows suspicious low attenuations in the pons and bilateral brachium pontis.
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